I have seem to see the term "Fast Idle" used a great deal lately. My question is: What is the intended purpose for it and when do you guys use your Fast Idle feature? Lets say you pull into a parking lot to go inside a business for 5 to 10 minutes at the most and want or need to leave the bus running, do you fast idle it then or just regular idle? What about the few minutes while you are refueling? What about the 20 to 30 minutes when you pull off the highway to grab a bite to eat? So far, I've just used my fast idle when the bus is warming up before a drive or when I need to idle the bus for any longer than 15 minutes. I know it is best to shut the engine down completely and not idle it at all but when the time comes to leave the bus running, when is the correct time to use fast idle and not to use fast idle? I'd just like to know how everyone else handles their Fast Idle situations....Thanks..
As I have already pointed out on another thread I have a disfunctional fast idle through my King Cruise. It sounds like that may be fixable but ... I don't see much need for it. We don't have coach air so there's no reason to leave the engine running when we stop. We don't plan to go where its cold anymore so there's no need to warm it up anymore either. And 2-strokes don't really warm up on fast idle anyway. My preference is to shut it off. To answer your question more directly - if you have bus air then you may need to fast idle. Otherwise you might as well shut it off - you'll be doing your wallet as well as your neighbours a favour.
I have a pd4903, similar to 4905. The road air and heat works fine. When I set park brake with air or heat on the fast idle automatically comes on . Keeps engine running fast enough to keep batteries charged with the two blower fans running.
Big John
Many on this board advise not idling any more than is absolutely necessary-- that goes for normal as well as fast idle. Greyhounds needed that fast idle to keep everyone inside hot or cold while at terminals etc. My fast idle is set at 800rpm and would only be used to air up a bit faster. I seem to be getting into the practice now of airing up with an electric compressor though.
One thing fast idle will do is keep your engine from loading.
When fuel was $4.00 a gallon, slow idle speed cost you 8 cents a minute.
On high idle, it was more.
Unless the engine is pushing you down the road, maybe best to turn it off?
Not to mention the unwanted attention of the anti-idling contingent.
My decisions?
I'll fast idle the engine if whatever is connected to the engine needs a higher RPM for its function.
So, the stock HVAC needs electricity, coolant flow, compressor spin, all of which work better at a higher engine RPM.
Building air more quickly without a foot on the throttle.
Driver trainer in me, and the reality of memory fading as the years go by...always a good feeling to hear the high idle kick on as the coach is parked....means it is out of gear and the parking brake is engaged.
You go through the motions of parking, and the coach answers with the reward of a change in engine note.
Do you need one in a coach conversion? Not really.
happy coaching!
buswarrior
I use mine to pull the heat out of the engine when I come off the road before I shut it down. The turbo and heads need about a minute to drop the temps down before I shut down. I use it to build air too, but thats about it.
Interesting comments; Is the fact that my 8-71 doesn't hold much oil pressure at low idle an issue?
Dennis
Quote from: Hi yo silver on February 03, 2009, 02:30:55 PM
Interesting comments; Is the fact that my 8-71 doesn't hold much oil pressure at low idle an issue?
Dennis
This is what my GM RTS manual states:
QuoteNormal readings with the engine hot are: idling 9-18psi and at governed full load speed 50-70psi. To help avoid engine damage, the engine must not be operated when the oil pressure falls below 20psi at governed speed under full load.
On the issue of idling/fast idling it says:
QuoteIf you plan to park for more than a minute or two or to leave the coach, shut off the engine. If idling is absolutely necessary due to the nature or conditions of the run, try to maintain 1000 engine rpm (Fast Idle).
hth
QuoteHighTechRedneck
This is what my GM RTS manual states:
On the issue of idling/fast idling it says:
If you plan to park for more than a minute or two or to leave the coach, shut off the engine. If idling is absolutely necessary due to the nature or conditions of the run, try to maintain 1000 engine rpm (Fast Idle).
hth
Thanks for the info. Thats exactly what I was looking for. It looks like I have already been using it for its intended purpose but wasn't sure.